Publications

Low plasma ergothioneine levels are associated with neurodegeneration and cerebrovascular disease in dementia

Ergothioneine (ET) is a dietary amino-thione with strong antioxidant and cytoprotective properties and has possible therapeutic potential for neurodegenerative and vascular diseases. Decreased blood concentrations of ET have been found in patients with mild cognitive impairment, but its status in neurodegenerative and vascular dementias is currently unclear. To address this, a cross-sectional study was conducted on 496 participants, consisting of 88 with no cognitive impairment (NCI), 201 with cognitive impairment, no dementia (CIND) as well as 207 with dementia, of whom 160 have Alzheimer's Disease (AD) and 47 have vascular dementia. All subjects underwent blood-draw, neuropsychological assessments, as well as neuroimaging assessments of cerebrovascular diseases (CeVD) and brain atrophy. Plasma ET as well as its metabolite l-hercynine were measured using high sensitivity liquid chromatography tandem-mass spectrometry (LC-MS/MS). Plasma ET concentrations were lowest in dementia (p < 0.001 vs. NCI and CIND), with intermediate levels in CIND (p < 0.001 vs. NCI). A significant increase in l-hercynine to ET ratio was also observed in dementia (p < 0.01 vs. NCI). In multivariate models adjusted for demographic and vascular risk factors, lower levels of ET were significantly associated with dementia both with or without CeVD, while ET associations with CIND were significant only in the presence of CeVD. Furthermore, lower ET levels were also associated with white matter hyperintensities and brain atrophy markers (reduced global cortical thickness and hippocampal volumes). The incremental decreases in ET levels along the CIND-dementia clinical continuum suggest that low levels of ET are associated with disease severity and could be a potential biomarker for cognitive impairment. Deficiency of ET may contribute towards neurodegeneration- and CeVD-associated cognitive impairments, possibly via the exacerbation of oxidative stress in these conditions.

Measurement of protein carbonyls in human brain tissue

The carbonyl assay has been developed as a general assay of oxidative protein damage to assess steady-state protein damage in animal tissues and body fluids. The assay is based on the fact that several ROS can attack amino acid residues in proteins (particularly histidine, arginine, lysine, and proline) to produce carbonyl functions that can react with 2,4-dinitrophenylhydrazine (DNPH) to generate chromophoric dinitrophenylhydrazones. This reaction can, therefore, be used to estimate the carbonyl content of proteins in human tissues and body fluids. Western blotting assays based on the use of anti-dinitrophenol antibodies have also been developed to identify oxidatively damaged proteins in tissues and body fluids after their extraction and derivatization with DNPH. The carbonyl assay has become widely used and many laboratories have developed individual protocols for it. Sometimes, the assay procedures used are not precisely specified, and when they are, they may differ from those originally proposed by the group of Stadtman et al. This point is important, because there is considerable variation in the baseline levels of protein carbonyls in certain tissues, depending on how the assay is performed.

The identification of antioxidants in dark soy sauce

Soy sauce is a traditional fermented seasoning in Asian countries, that has high antioxidant activity in vitro and some antioxidant activity in vivo. We attempted to identify the major antioxidants present, using the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay as a guide. 3-Hydroxy-2-methyl-4H-pyran-4-one (maltol) was one of several active compounds found in an ethyl acetate extract of dark soy sauce (DSS) and was present at millimolar concentrations in DSS. However, most of the antioxidant activity was present in colored fractions, two of which (CP1 and CP2) were obtained by gel filtration chromatography. Their structural characteristics based on nuclear magnetic resonance (NMR) and electrospray-ionization time-of-flight mass spectrometry (ESI-TOF-MS) analysis suggest that carbohydrate-containing pigments such as melanoidins are the major contributors to the high antioxidant capacity of DSS.

Prevention of Peroxynitrite-Dependent Tyrosine Nitration and Inactivation of α₁-Antiproteinase by Antibiotics

Peroxynitrite, formed by reaction of superoxide and nitric oxide, appears to be an important tissue damaging species generated at sites of inflammation. In this paper, we compare the abilities of several antibiotics to protect against peroxynitrite-dependent inactivation of α1-antiproteinase, and to inhibit tyrosine nitration by peroxynitrite, in vitro. Tetracycline, minocycline, doxycycline, rifamycin and rifampicin were highly-protective in both assay systems, whereas several other antibiotics tested were not. The possibility that antibiotics could affect tissue injury at sites of inflammation by scavenging peroxynitrite is discussed.

The anti-inflammatory effects ofd-myo-inositol-1.2.6-trisphosphate (PP56) on animal models of inflammation

No abstract is provided for this article.

The role of superoxide and hydroxyl radicals in the degradation of DNA and deoxyribose induced by a copperphenanthroline complex

DNA degradation by a copper(II)-phenanthroline complex was studied in the presence of NADH, 2-mercaptoethanol or a mixture of hypoxanthine and xanthine oxidase, which generates the Superoxide radical, O2 −. In all cases degradation was prevented by catalase but not by scavengers of the hydroxyl radical, OH.. It remains possible, however, that OH. was generated in close association with DNA so that the scavengers could not remove it before it reacted. Superoxide dismutase inhibited DNA degradation at low copper(II) phenanthroline concentrations in the presence of NADH or hypoxanthine-xanthine oxidase, but not at higher complex concentrations. Superoxide dismutase had little effect on DNA degradation in the presence of 2-mercaptoethanol. The role of oxygen radicals in the DNA degradation induced by copper(II) phenanthroline is discussed.

Metabolic signatures of renal cell carcinoma

Antioxidant Action of Benzylisoquinoline Alkaloids

The antioxidant action of a series of benzylisoquinoline alkaloids has been investigated. Laudanosoline, protopapaverine, anonaine, apomorphine, glaucine, boldine, bulbocapnine, tetrahydroberberine and stepholidine produced a dose-dependent inhibition of microsomal lipid peroxidation induced by Fe2+/ascorbate, CCl4/NADPH or by Fe3+ADP/NADPH. Apomorphine exerted the highest inhibitory effects in the three systems of induction used, with a potency higher than propyl gallate. Laudanosoline was particularly effective in the first system, while bulbocapnine and anonaine were more potent when CCl4/NADPH or Fe3+ -ADP/NADPH were used as inducers. Laudanosoline, protopapaverine, apomorphine, tetrahydroberberine and stepholidine were also potent inhibitors of nitroblue tetrazolium (NBT) reduction. The presence of a free hydroxyl group or preferably of a catechol group is a feature relevant for inhibition of lipid peroxidation and NBT reduction, nevertheless the antioxidant activity of benzylisoquinoline alkaloids cannot be only ascribed to the formation of phenoxy radicals and other free radical species may be formed during aporphine and tetrahydroprotoberberine oxidation. The influence of this series of compounds on the time course of lipid peroxidation suggests that some of them, like apomorphine and boldine act as chain-breaking antioxidants.

Antioxidants: Molecules, medicines, and myths

Knockout of a putative ergothioneine transporter in<i>Caenorhabditis elegans</i>decreases lifespan and increases susceptibility to oxidative damage

In addition to excretion of metabolic waste products, organic ionic transporters facilitate uptake of specific compounds of physiological importance. In animals, the organic cation transporter, OCTN1 was found to enable the specific uptake of the unique amino acid, ergothioneine (EGT). EGT can accumulate in the body at up to millimolar concentrations and is believed to function as a physiological antioxidant. However the main function of EGT and the reasons for its active accumulation in the body remain obscure. Through bioinformatic approaches, we identified an analogous EGT transporter in the nematode, Caenorhabditis elegans. The present study investigated and characterized deletion mutants of this gene, OCT-1, in the nematodes. Gene deletion mutations of the OCT-1 transporter were shown to decrease overall lifespan of the worms and increase oxidative damage. However the absence of impaired EGT uptake and the inability of excess EGT to rescue the debilitating phenotype indicate that EGT transport does not explain the deleterious effects of the gene deletion.

Chronic infections and coronary heart disease

Metal ion activation of dioxygen

Superoxide‐dependent formation of hydroxyl radicals in the presence of thiol compounds

No abstract is provided for this article.

Interference with ubiquitination causes oxidative damage and increased protein nitration: implications for neurodegenerative diseases

Abstract Inhibition of the proteasomal pathway for degrading abnormal proteins leads to protein aggregation, increased oxidative damage and increased protein nitration. We now show that interference with polyubiquitination has similar consequences. Expression of a dominant‐negative mutant form of ubiquitin (K48R) in NT‐2 and SK‐N‐MC cells caused decreased cell growth rates and increased oxidative damage (protein carbonyls and lipid peroxidation), nitric oxide production and elevated protein nitration. It also rendered cells highly sensitive to 4‐hydroxy‐2,3‐ trans ‐nonenal, a neurotoxic end‐product of lipid peroxidation, hydrogen peroxide and deprivation of growth factors. Overexpression of wild‐type ubiquitin did not produce these effects. Our data show that interference with the ubiquitin‐proteasome pathway at a different point and by a different mechanism can produce many of the common features of human neurodegenerative diseases, such as increased lipid peroxidation, protein oxidation and protein nitration. We suggest that defects in this pathway at multiple points could produce the common features of neurodegenerative diseases, and that more such defects remain to be discovered.

Redox chemistry: the essentials

6‐Hydroxydopamine increases the hydroxylation and nitration of phenylalanine <i>in vivo</i>: implication of peroxynitrite formation

In the present study, we investigated the effect of the dopaminergic neurotoxin 6‐hydroxydopamine (6‐OHDA) on hydroxyl free radical and peroxynitrite formation in vivo using d ‐phenylalanine as a novel mechanistic probe. In vivo microdialysis was carried out in the striatum of freely moving male Wistar rats. The microdialysis probes were perfused with artificial cerebrospinal fluid containing 5 m m d ‐phenylalanine (flow rate 2 µL/min). After obtaining a stable baseline 6‐OHDA was delivered into the striatum via reverse microdialysis for 60 min. HPLC measurements of the effluent were performed using photodiode array detection for determination of phenylalanine derived o ‐tyrosine and m ‐tyrosine (as hydroxylation markers) as well as of nitrotyrosine and nitrophenylalanine (as nitration markers). The basal levels of the hydroxylation derived products of phenylalanine were approximately 100‐fold higher than those of the nitration derived products. 6‐OHDA (0.1, 1, 10 m m ) significantly increased o ‐ and m ‐tyrosine up to nine‐ and 13‐fold, respectively, whereas levels of 3‐nitrotyrosine and 4‐nitrophenylalanine were significantly increased up to 422‐ and 358‐fold, respectively. The results demonstrate that phenylalanine is a sensitive in vivo marker for 6‐OHDA‐induced hydroxylation and nitration reactions which are clearly concentration dependent. We conclude that peroxynitrite formation is involved in 6‐OHDA‐induced neurochemical effects.

Photosynthesis: Physical Mechanisms and Chemical Patterns

No abstract is provided for this article.

Oxygen Radicals and Human Disease

Toxic oxygen free radicals have been implicated as important pathologic mediators in many clinical disorders. We discuss the chemistry of oxygen radical production and the roles of iron and of various antioxidants as well as the diseases that have received active attention in oxyradical research. Particular attention is focused on cigarette smoke oxidants, ischemia-reperfusion-induced radical production, carcinogenesis, and aging. Such research may well provide a firm foundation for therapeutic breakthroughs.